ICF gable walls

[deuce22]

Hi.

 

Can somebody that has built with ICF let me know if the gable walls were cut from wall plate height or if the thickness of the rafter was added as well. I've never constructed with it before, but I'm about to start adding the gables.

If I cut from the height of the wall plate then add the 7x2 rafters, there will not be any wall in between the ladder rafters, like there is with blockwork.  If I add it on then I will need to leave a void to allow me to cut through the polystyrene to attach the ladies for the last rafter. If this is the case then it would be easier to just attach some PIR insulation after.

 

 

Thanks.

[Russell griffiths]

I would just leave a void, bigger than what you need, then after you fit the ladder fill around it with a bucket of concrete. 

Probably need to isolate the concrete from the timber by wrapping the timber or painting it. 

@willbish how did you do yours. 

[willbish]

I don't have much of an over hang on my gable.

So after the concrete was poured I fixed a rafter to the outer face of the ICF, mechanical fix. The OSB sarking is nailed to this outer rafter and then barge board fixed.

 

@deuce22 is a large overhang necessary?

You could extend the ridge steel out beyond the outer face and the wall plate too. Assuming the rafter length does not require a mid span perlin.

However you do it I think you will be introducing some pretty significant thermal bridging.

[Russell griffiths]

If you made a plywood former, you could put them in the cavity, and leave them in place so when you have filled with concrete the former stays in place and your ladder rails insert into the former and you screw it to the ply former. 

[Russell griffiths]

Not sure if that makes sense. 

[deuce22]

Hi Russell.

 

Yes what you suggested does make sense, but there's a lot more work involved, plus there will be thermal bridging through the trimmer. The roof will have vaulted ceilings.

 

I've decided to create a slight upstaged at the bottom of the gable wall. This will allow me to fit the last rafter on the internal side of the wall and be fully insulated. I will then do what Willbish did and chemically fit the ladder rafters to the outside of the wall.

 

Thanks both for your help.